Actually, clownbaby is right, that study is very very small and not enough to judge a supplement, let alone to make a decision about anything.
However, since I've been taking ZMA for a couple/few months and have enough for 6 months and I love the effects which are:
-Better Sleep
-Sh*t every morning (this is because of the magnesium, a lot of people on Atkins, Paleo diets, etc... also supplement with magnesium, considering I only eat meat, no fruits, vegetables or grains, this is a good benefit.
-better overall being.
-I need the extra zinc because I lose more than average.